Sounds like you've got a bit of burnout. I felt like this a while back, I got though it by working for a company I really felt I had an impact and enjoyed the work culture.
I'd counter argue that leaving London doesn't have to mean the end of a career. Have you tried looking at other places in the UK to live/work? I'm a bit bias but Bristol is a fantastic city to live in and the tech scene is really well developed. Lots of start ups, mid sized and large companies. Plenty of banks/fin tech companies are based here too.
One of the things that have helped me get though burnout was to do other things outside of work. Be that go for food, cinema or even visiting tourist sites.
https://www.amazon.co.uk/Empireworld-British-Imperialism-Sha...